There presently exists a wide variety of printing apparatuses utilizing fluid jet technology. Typically, such prior art apparatuses provide a linear array of fluid jet orifices formed in an orifice plate from which filaments of pressurized marking fluid (e.g., ink, dye, etc.) are caused to issue. An individually controllable electrostatic charging electrode is disposed downstream in registry with each orifice along the so-called "drop formation" zone. In accordance with known principles of electrostatic induction, the fluid filament is caused to assume an electrical potential opposite in polarity and related in magnitude to the electrical potential of its respective charging electrode. When a droplet of fluid is separated from the filament, this induced electrostatic charge is then trapped on and in the droplet.
According to conventional procedures, fluid jet orifice plates have been constructed utilizing standard techniques borrowed from the semiconductor industry for the manufacture of semiconductors, etc. (see, e.g. Maissel et al, Handbook of Thin Film Technology, McGraw-Hill, Inc., Chapter 7 (1970), the disclosure thereof being expressly incorporated hereinto by reference).
A conventional prior art procedure for making fluid jet orifice plate 10 is depicted in FIGS. 1a-1e. A substrate 12 of copper or copper alloy is coated on its front and back sides, 11, 13, respectively, with a suitable photoresist material 14 and covered with an exposure mask 16. Thereafter, the structure is exposed to light so as to develop areas bordering the circular masked areas 18 which will eventually define the orifice locations. The light exposed photoresist material is then removed from the substrate utilizing appropriate chemical wash compounds thereby leaving unexposed pegs 20 which were in registry with areas 18 of mask 16. The back side 13 of substrate 12 is treated in a similar manner so as to leave pegs 20 of a larger diameter and in registry with the smaller diameter pegs 20 on the front side 11.
Both sides of the substrate are thereafter electroplated with crystalline nickel 22, the nickel being deposited on the substrate on the areas from which the exposed photoresist was washed and thus not deposited on the pegs. The pegs on each side of the substrate are then dissolved and the copper substrate thereunder is preferentially etched form each side so as to form a hole 24 through the substrate connecting the front and back sides with the nickel coating defining the orifice 26.
The ink for typical ink jet apparatuses has been developed for paper printing and thus such ink formulations are chosen (insofar as possible) so as to be noncorrosive and benign to both the electroform crystalline nickel and the typical substrate of copper or copper alloy. Recently, however, fluid jet technology has expanded and applications have been identified in the textile industry (see, e.g., my copending U.S. patent application Ser. Nos. 231,326 filed Feb. 4, 1981 and 393,698 filed June 30, 1982). Such textile applications demand that fluids be compatible with the requirements of the fabric substrate onto which the fluid is applied. Oftentimes, however, the fluids typically required for textile applications are (to a somewhat greater extent than for paper printing) corrosive to both the copper or copper alloy orifice plate substrate and/or the crystalline nickel plated thereon. There are a great number of corrosive fluids typically encountered in textile applications and well known to those skilled in the textile arts which must be substantially benign to any fluid jet orifice plate in contact therewith.
Thus, conventional orifice plates are oftentimes inadequate and as a result a distinct need exists for orifice plates which are chemically stable (e.g., noncorrosive) in the presence of a wide range of chemical substances normally encountered in the textile industry. It is believed that until the present invention such need went unanswered.
The present invention specifically addresses the corrosive nature of certain fluids utilized in fluid jet apparatuses in textile applications by providing an orifice plate of improved construction. In accordance with the present invention, such advantageous qualities are realized by depositing amorphous nickel- or cobalt-phosphorus alloys onto a highly corrosion resistant substrate.
The reader should also appreciate that many critical parts for devices having one relatively thin dimension are typically made by a process of photofabrication. One such part is a fluid jet orifice plate for a fluid jet printing apparatus as briefly described above. In the photofabrication process, the substrate to be photofabricated is coated with a thin light-sensitive material called "photoresist" and exposed by means of light, usually blue or ultraviolet light to form an exposure pattern thereon. The light either degrades the photoresist to make it selectively soluble in a suitable solvent or cross links the molecules in the photoresist so as to make it selectively insoluble. In any case after exposure and development (so as to selectively remove soluble photoresist) a thin film of foreign material in a preselected pattern exists on the substrate to be photofabricated. At this point, a selective coating may be plated on the exposed substrate portions and the photoresist removed, or the substrate may go directly to the next step without such an intermediate plating step.
In the next step, the objective is to subject the substrate to an etchant that selectively attacks the substrate material. The photoresist in one case or the overplating in the other must not be attacked by the etchant. When a suitable etchant is found, the substrate to be etched experiences metal dissolution in the areas where the metal is exposed, the metal thus remaining where it is covered by protective material in the form of photoresist or overplating (e.g. see discussion above with regard to FIGS. 1a-1e).
It can be appreciated that most photoresist materials are thin plastic coatings such that as etching occurs and as they are undercut, the coatings pull away from the substrate and tend to detach in an intermittent fashion so as to give a ragged or irregular edge.
Electroplated masks that protect the substrate during etching as above are usually of metal and it can be appreciated that although they are rigid and resist detachment, must be resistant to the etchant so as to perform their intended masking function. In the case of materials such as stainless steels, titanium, zirconium, hafnium, tungsten, molybdenum, Monel metals, or some of the Hastelloys, it is very difficult to find a material for a mask that is selectively etched by known etchants. Thus, according to another aspect of this invention, a new and unexpected result of photoetchant protection by an alloy yields selective etching of a number of materials that have been found difficult to photoetch in the past and thus renders the present invention particularly suitable to photoetching masks having the desired exposure pattern formed therein.
The substrates advantageously utilized in accordance with the present invention can be any material which is highly corrosion resistant and thus is stable in contact with aqueous solutions for sustained periods of time. Suitable substrate materials can include, for example, Monel metals (e.g., copper-nickel alloys), ferritic stainless steels (e.g., stainless steel having low nickel content), titanium, zirconium, and martinsitic stainless steels. Of these suitable substrate materials, the stainless steels are preferred due to the relative ease with which etching can be accomplished (e.g., removal of the substrate after plating to form the openings in communication with the orifice). Similarly, the Monel metals can be preferentially etched by ferric chloride with the added advantage that less etch times are required.
As used herein the terms "preferential" etching, "selective" etching or like terms are meant to refer to etching of the substrate material without affecting the plated amorphous alloy layer.
Zirconium and titanium can be preferentially etched by utilizing hydrofluoric acid further acidified with hydrochloric acid. Bonding adhesion of the amorphous nickel- or cobalt-phosphorus alloy to titanium can be assured by preliminarily etching the surface thereof with hydrochloric acid in solution with an ethylene glycol combination and, thereafter, striking the surface with a copper cyanide strike. The "glassy" amorphous nickel- or cobalt-phosphorus alloy will securely adhere to the copper strike. Furthermore, zirconium may be initially prepared by plating the surfaces thereof in a Watts nickel bath, the surfaces being preliminarily treated in a soaking bath of hydrofluoric acid and acid salt. Amorphous nickel will therefore more readily adhere to the Watts nickel plating. Various other surface preparation procedures and techniques may be advantageously utilized and are believed to be well within the ordinary skill of those in the art.
The reader may wish to refer to the following U.S. patents to glean further background information: U.S. Pat. Nos. 4,108,739 to Tadokoro et al; 3,041,254 to Pepler; 3,041,255 to Passal et al; 2,069,566 to Tuttle; 3,303,111 to Peach; 3,475,293 to Haynes et al; 3,658,569 to Phillip et al; 3,759,803 to Du Rose et al; 4,086,149 to Martinsons et al; 4,113,248 to Yanagioka; 4,127,709 to Ruben; and 4,224,133 to Takahashi.